Generally, a hydraulic excavator is known as a typical example of construction machines, and this hydraulic excavator is constituted by an automotive lower traveling structure, an upper revolving structure which is swingably mounted on the lower traveling structure, and a working mechanism liftably mounted on the front side of the upper revolving structure.
The upper revolving structure is largely constituted by a revolving frame serving as a supporting structure, a cab which is provided on the front side of the revolving frame and in which an operator rides, an engine which is mounted on the rear side of the revolving frame to drive a hydraulic pump, heat exchange device provided in the vicinity of the engine, and an exterior cover for covering the engine, the heat exchange device, and the like.
Here, the heat exchange device is constituted by a plurality of heat exchangers, such as a radiator, an oil cooler, an intercooler, and the like, which are opposed to a cooling fan of the engine. In addition, in small-size hydraulic excavators in recent years, the radiator, the oil cooler, the intercooler, and the like are arranged in parallel to the flowing direction of the cooling air (in juxtaposition in the widthwise direction) in order to make effective use of the limited space of the upper revolving structure (see, for example, Patent Literature 1: Japanese Patent Laid-Open No. 2006-207862).
Meanwhile, in cases where the number of heat exchangers has increased or the installation space of the heat exchange device has become even smaller, not all the heat exchangers can be disposed in parallel. For this reason, among the heat exchange device, there is a type which is configured such that another heat exchanger is disposed overlappingly in series with a plurality of heat exchangers juxtaposed in parallel on the upstream side in the flowing direction of the cooling air (see, for example, Patent Literature 2: Japanese Patent Laid-Open No. 2006-224812).
Incidentally, with the hydraulic excavator according to the above-described Japanese Patent Literature 2, another heat exchanger is disposed overlappingly in series with the flowing direction of the cooling air on the upstream side of one group of heat exchangers juxtaposed in parallel. For this reason, cooling air which has become warm after passing through the upstream-side heat exchanger is supplied to the one group of heat exchangers located on the downstream side of the cooling air. For this reason, there is a problem in that, among the downstream-side heat exchangers, those portions that overlap with the upstream-side heat exchanger are poor in the cooling efficiency.